Semiconductor laser diodes have found applications in a wide variety of information handling systems because of their compact size and because their technology is compatible with that of the associated electronic circuitry. They are being employed in areas such as data communications optical storage and optical printing. Most commonly used are group III/V compound materials. Particularly AlGaAs lasers have found extensive usage.
Historically, the mirror facets which define the length of the laser's cavity have been obtained by cleaving the laser bars, i.e., layered structures comprising the active waveguide of the device. Cleaving usually provides single often high quality devices which require, however, further individual processing, such as mirror passivation, and testing. Due to these additional processing steps for each individual laser diode their fabrication and testing costs are unreasonably increased.
More recently, there is a strong trend to increase the scale of integration which requires the replacement of at least one cleaved mirror facet of the laser diodes by an etched mirror. Since substantial progress has been made in obtaining good quality etched mirrors, this technology appears to be very promising. It allows processes like mirror coating and testing to be performed on the full-wafer level, with the benefit of reduced handling, increased yield, and decreased fabrication and testing costs. In addition, etching laser mirrors allows for the monolithic integration of various other devices on the same substrate.
A technique has been reported on in the article "AlGaAs Lasers with Micro-Cleaved Mirrors Suitable for Monolithic Integration", H. Blauvelt et al., Applied Physics Letters, Vol. 40, No. 4, February 1989, pp. 289-290, for cleaving the mirrors of AlGaAs lasers without cleaving the laser's substrate. Such a micro-cleaved laser diode allows the monolithic integration of other electronic devices on the same substrate. A laser diode with microcleaved facet is described being separated from the GaAs substrate by an intermediate AlGaAs layer with high aluminum content. The thermal resistance of the structure is increased due to this AlGaAs layer with high Al content and the growth of epitaxial layers on top of this layer is made more difficult. Before cleaving the facet, the epitaxially grown layers of the laser are underetched by selectively etching the AlGaAs intermediate layer. This etch step provides for a cantilever structure which can be cleaved. The position of the micro-cleaved facet is defined by the end of the etch groove under the cantilever. A main drawback of this technique is that the length of the cantilever, and therewith the position of the facet to be cleaved, strongly depends on the concentration of the etchant and the etch time. Caused by this fact, the length of the laser's cavity, determined by the position of the facets, cannot be precisely defined.